The Italian Quantum Backbone (IQB) is a national fiber-optic infrastructure connecting the
Italian National Metrology Institute (INRIM) with research centers and laboratories across Italy,
spanning over 1,800 km.
Originally developed to distribute high-accuracy time and frequency signals, the IQB has
evolved into a versatile platform supporting advanced experiments in quantum communication,
distributed sensing, and more.
High-Precision Time Distribution
- A large portion of the IQB supports the distribution of precise time signals using the White
Rabbit Precise Time Protocol. Connected laboratories receive Nanosecond-level
accurate time signals and 10 MHz radio frequency signals with high stability - This solution offers a scalable, robust, and secure alternative to satellite-based timing
systems.
Ultra-Coherent Laser Signal Distribution
- One of the standout features of the IQB is the distribution of ultra-coherent laser signals
among research labs - A narrow-linewidth laser (~1550 nm) originates from INRIM in Turin, and its frequency is
measured against national standards with high accuracy. The signal is distributed without
loss of coherence, thanks to advanced interferometric techniques that compensate for
fiber deformations in real time - This system supports ultra-high-precision applications requiring exceptional signal
accuracy and stability.
Quantum Experimentation Support
- To enable quantum research, one of the two fibers along much of the IQB is kept free from
classical signals. This fiber is reserved for transmitting single-photon signals, which are
extremely weak and sensitive to cross-talk with classical signals travelling into the same
fiber.
Access Points and Coverage
- Access to the IQB is available through connected research laboratories or access
points located every 80 to 100 km, which also function as signal amplification and
regeneration sites - These access points make the infrastructure widely available to the national and
European research communities.
Fundamental Metrology
Since 2021, INRIM is connected to major European national metrology institutes in France,
the United Kingdom, and Germany. This international network has enabled the largest
comparisons of optical clocks ever performed, involving over 10 optical clocks of different
atomic species across 7 laboratories.
These comparisons are critical for:
- Advancing theoretical and experimental atomic physics
- Supporting the ongoing redefinition of the SI second
- Validating and complementing satellite-based time transfer techniques
Using the IQB, INRIM has also demonstrated how distributing metrological signals via fiber can
support high-resolution spectroscopy and Very Long Baseline Interferometry
Quantum Communication
IQB plays a key role in the European Quantum Communication Infrastructure (EuroQCI) — an
EU initiative aimed at securing sensitive communications (e.g., government services and critical
infrastructure) through quantum key distribution.
INRIM coordinates the QUID project (Quantum Italy Deployment), which:
- Develops and deploys quantum communication technologies
- Focuses on integration with classical communication systems
- Has extended IQB by building nine metropolitan quantum networks
- Implements EuroQCI-aligned case studies
Thanks to its hybrid design, IQB supports both metrological services and quantum
communication, enabling powerful synergies. INRIM has shown that high-precision
synchronization of distant nodes and Ultra-coherent optical signal distribution are crucial
enablers for advanced quantum protocols, such as the twin-field Quantum Key Distribution in
real-world environments.
Distributed Sensing
Fiber-optic networks are increasingly recognized as valuable tools for environmental monitoring.
Using fibers as sensors offers broader and denser geographic coverage than traditional
systems and has great potential for early-warning systems, critical infrastructure monitoring,
and seismic activity detection
INRIM has demonstrated that ultra-coherent optical signal distribution techniques can be
effectively adapted for this purpose.
INRIM leads the SENSEI project (Smart European Networks for Sensing the Environment
and Internet quality), which aims to:
- Develop technologies that turn fibers into a distributed sensing platform
- Enhance data transmission quality by integrating real-time infrastructure monitoring
- Perform field tests of novel photonic sensing techniques. The IQB is a unique testbed for
this task, covering challenging environments such as submarine areas, seismic zones
and densely populated regions